Interposer with extruded feed-through vias

ABSTRACT

A method of forming interposers includes positioning a plurality of extruded metal wires across a first platten and second platten, which secures the extruded metal wires. A sealing material is added to sidewalls of a volume having the plurality of extruded metal wires within, with the first and second plattens as end plates to form a holding volume. The holding volume is filled with a filling material. The filling material is heated to a sufficient temperature to form a heat treated filled volume. After removing the sealing material, the heat treated filled volume is sawed into a plurality of slices having a predetermined thickness to form a plurality of interposer substrates having a plurality of feed-thru conducting features provided by the plurality of extruded metal wires.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Provisional Application Ser. No. 61/,607,236 entitled “LOW COST INTERPOSER MANUFACTURING”, filed Mar. 6, 2012, which is herein incorporated by reference in its entirety.

FIELD

Disclosed embodiments relate to interposers for semiconductor devices and methods for manufacturing interposers.

BACKGROUND

An interposer is an electrical interface providing routing between one socket or connection to another. The purpose of an interposer is generally to spread a connection to a wider pitch or to reroute a connection to a different connection. A typical interposer example application is for providing routing between an integrated circuit (IC) die to a ball grid array (BGA) on a substrate, such as the IC die on the interposer on a BGA substrate.

In a conventional method for forming interposers, through-vias are formed, which are dielectric lined, and then the dielectric lined vias are filled with a metal. For example, a silicon wafer may be thinned, such as from a thickness of about 800 μm to about 150 to 250 μm to remain rigid enough still be able to handled without a support carrier. Silicon through-vias are then formed by deep reactive ion etching (DRIE) process. A convention DRIE process is a Bosch process for forming through vias in silicon substrates which uses a fluorine based plasma chemistry to etch the silicon, combined with a fluorocarbon plasma process to provide sidewall passivation and improved selectivity to masking materials. A complete etch process cycles between etch and deposition steps many times to achieve deep, substantially vertical etch profiles. The Bosch process offers higher etch rates, but at the cost of sidewall roughness in the form of scalloping.

A dielectric layer (e.g., SiO₂) is then formed by conventional thermal oxidation or a deposition process to dielectric line the through-vias. Alternatively, use of a dielectric (e.g., glass) substrate allows through-via formation without the need for a dielectric lining.

In the case of silicon substrates, through-silicon vias (TSVs) are then formed by filling the dielectric lined vias, such as by a copper (Cu) seed layer followed by Cu electroplating, and then planarization using chemical mechanical polishing (CMP). For dielectric substrates, the through-vias are analogously metal filled.

Multilayer wiring on one or both sides of the interposer can then be formed by Cu plating using a conventional semi additive process (SAP). Micro bumps can then be fabricated on the top side of the interposer by electroplating, which allows IC chip(s) to be mounted on the top side of the interposer.

SUMMARY

Disclosed embodiments include methods of forming interposers and interposers therefrom. Disclosed methods include positioning a plurality of extruded metal wires across a first platten and second platen which secure the wires. As used herein, the term “metal wires” includes metal alloy wires, and coated metal wires. A sealing material is added to sidewalls of a volume having the extruded metal wires within, with the first and second plattens as end plates to form a holding volume which functions to hold a filling material or a filling material precursor. The holding volume can then be filled through an aperture in the holding volume (e.g., in the top of the holding volume) with a dielectric filling material (e.g., a powder). Alternatively, the extruded metal wires can have a dielectric coating thereon, which allows the filling material to be a non-dielectric material, such as a semiconductor material.

The filling material is heated to a sufficient temperature to form a heat treated filled volume. The sealing material is removed, and the heat treated filled volume is then sawed into a plurality of slices having a predetermined thickness to form a plurality of interposer substrates having a plurality of feed-thru conducting features provided by the plurality of extruded metal wires.

As used herein “extruded metal wires” as known in the art of metallurgy refers to a crystal structure which evidences a preferential orientation and elongation of the crystal (nonrandom distribution of crystal orientation), being a preferential crystal orientation resulting from the extrusion manufacturing process where the crystals become preferentially aligned and elongated along the extrusion direction. The extrusion direction corresponds to the length direction of the disclosed extruded metal wires which provide the feed-through vias for the interposer.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, wherein:

FIG. 1 is a flow chart that shows steps in an example method for forming interposers having extruded metal wires providing feed-through vias, according to an example embodiment.

FIGS. 2A-D depict process progression for the example method of forming interposers having extruded metal wires providing feed-through vias described relative to FIG. 1.

FIG. 2E depicts a top view of an example interposer substrate having extruded metal wires providing feed-through vias obtained after sawing.

FIG. 3 is a cross sectional depiction of an example interposer substrate including extruded metal wires providing feed-through vias, according to an example embodiment.

DETAILED DESCRIPTION

Example embodiments are described with reference to the drawings, wherein like reference numerals are used to designate similar or equivalent elements. Illustrated ordering of acts or events should not be considered as limiting, as some acts or events may occur in different order and/or concurrently with other acts or events. Furthermore, some illustrated acts or events may not be required to implement a methodology in accordance with this disclosure.

FIG. 1 is a flow chart that shows steps in an example method 100 for forming interposers having extruded metal wires providing feed-through vias, according to an example embodiment. Step 101 comprises positioning a plurality of extruded metal wires across a first platten and second platen which secures the extruded metal wires. FIG. 2A depicts extruded metal wires 203, which can comprise strand copper wires as example metal wires across two plattens 206 and 207 in a desired (pattern) density.

As noted above, extruded metal wires 203 may also comprise a metal alloy. The extruded metal wires 203 may also include a non-oxidizing metal layer coating the extruded metal wires 203, such as a Pd or Pt coating layer. Plattens 206, 207 can take any shape, and are shown round only for illustration. Plattens 206, 207 generally include holes sized for the extruded metal wires 203 to be fit therethrough. The pattern of metal wires 203 can be uniform or non-uniform. An example platten material is stainless steel, but the platten material can vary depending on the materials that will be heat processed.

Step 102 comprises adding a sealing material 212 to sidewalls of a volume the plurality of extruded metal wires within, with the first and second plattens 206, 207 as end plates to form a holding volume. The holding volume is configured to prevent the filler material or filler material precursor from escaping. Example sealing materials 212 include stainless steel and titanium. The sealing material can be configured as a mold, and can also be fit together in a variety of ways including using a clamping mechanism, or fit with a locking pin. FIG. 2B depicts the sealing material 212 sealing the sidewall area of the cylindrical volume (holding volume) between the plattens 206, 207 to enable receiving (and holding) filling material as described below, typically by providing a top face having one or more apertures (not shown) to allow filling.

Step 103 comprises filling the sealed volume using aperture(s) provided. The filling material can comprise a powder or a viscous liquid, such as a monomer (precursor) of a thermoset resin. FIG. 2C depicts a holding volume after being filled with a filling material 217 which fills the holding volume between the extruded metal wires 203. The filling material 217 can be liquid or powder (e.g., soda lime glass powder, or a borosilicate powder).

Step 104 comprises heating the filling material to a sufficient temperature to form a heat treated filled volume. In the case of a powder, the sufficient temperature is at least equal to the softening point of the powder. In the case of a monomer, the sufficient temperature is high enough to cure (i.e., crosslink) the monomer. In one specific example the sufficient temperature is about 830° C. to be at or above the softening point of borosilicate glass. In the case of borosilicate glass and copper wires, the borosilicate glass softens below copper melting point (about 1080° C.).

Step 105 comprises sawing the heat treated filled volume into a plurality of slices having a predetermined thickness to form a plurality of interposer substrates having a plurality of feed-thru conducting features provided by the plurality of extruded metal wires 203. FIG. 2D depicts a saw blade 293 immediately before sawing the heat treated filled volume. A laser or other saw apparatus may also be used. The sawing can be configured to provide a desired interposer thickness typically in the range of 600 to 875 μm to accommodate conventional wafer (e.g., silicon wafer) handling equipment during assembly. A chemical mechanical polish (CMP) can also be incorporated to further smooth the top and/or bottom surface of the interposers if desired.

FIG. 2E depicts a top view of an example interposer substrate 290 obtained after removing the sealing material 212, and then sawing. Interposer substrate 290 includes extruded metal wires 203, and the filler material 217. A dielectric liner 218 is between the filler material 217 and the metal wires 203. The substrate 290 and dielectric liner 218 provide scallop-free vertical sidewalls along a full thickness of the through-vias occupied by the metal wires 203. As noted above, conventional Bosh etching leads to scalloped sidewalls. When the extruded metal wires 203 comprise copper, there can be a direct physical connection (no intervening seed layer) between the dielectric liner 218 and the extruded copper wires.

Advantages of disclosed methods from incorporating the through-vias (e.g., extruded metal wires) during the raw material manufacturing step which can reduce the chemistry and infrastructure needed to accommodate an electrically conductive feed-thru as compared to conventional methods for forming interposers that first form the through-vias in a substrate, and then fill the feed through-vias with a metal. For example, the need for DRIE etching of the vias is eliminated, as well as the need for metal deposition.

Disclosed interposers can include the option of adding one or more wiring layers (e.g., multilayer wiring) on one or both sides of the interposer for customizing routing patterns on one or both sides of the interposer. Subsequent steps to redistribute the feed-thru vias are also possible using contemporary patterning techniques available in backend of the line (BEOL) semiconductor processing, such as formation of a dielectric layer then a redistribution layers (RDL) thereon. On one example, multilayer wiring can be formed on one or both sides by metal (e.g., Cu) electroplating using a conventional semi additive process (SAP). Micro bumps can then be fabricated on the wiring layer by electroplating, which allows a bump pattern to be customized to match the bond pad pattern of IC chip(s) to be mounted on the interposer.

For example, FIG. 3 is a cross sectional depiction of an example interposer substrate 300 including extruded metal wires 203 providing feed-through vias, according to an example embodiment. A dielectric liner 218 is between the filler material 217 and the extruded metal wires 203. Interposer substrate 300 includes a top side RDL 310 and a bottom side RDL 315 which allow the routing pattern provided to be customized on respective sides of the interposer substrate 300.

Disclosed interposer substrates can be integrated into a variety of assembly flows to form a variety of different semiconductor devices and related products having one or more semiconductor die and one or more other substrates. The substrates can include organic or ceramic substrates. The semiconductor die may include various elements therein and/or layers thereon, including barrier layers, dielectric layers, device structures, active elements and passive elements including source regions, drain regions, bit lines, bases, emitters, collectors, conductive lines, conductive vias, etc. Moreover, the semiconductor die can be formed from a variety of processes including bipolar, CMOS, BiCMOS and MEMS.

Those skilled in the art to which this disclosure relates will appreciate that many other embodiments and variations of embodiments are possible within the scope of the claimed invention, and further additions, deletions, substitutions and modifications may be made to the described embodiments without departing from the scope of this disclosure. 

1. A method of forming interposers, comprising: positioning a plurality of extruded metal wires across a first platten and a second platten; adding sealing material to sidewalls of a volume having said plurality of extruded metal wires within, with said first and second plattens as end plates to form a holding volume; filling said holding volume with a filling material; heating said filling material to a sufficient temperature to form a heat treated filled volume, and sawing said heat treated filled volume into a plurality of slices having a predetermined thickness to form a plurality of interposer substrates having a plurality of feed-thru conducting features provided by said plurality of extruded metal wires.
 2. The method of claim 1, wherein said plurality of extruded metal wires comprise copper.
 3. The method of claim 1, wherein said filling material comprises a powder and said sufficient temperature results in heating said powder above its softening point.
 4. The method of claim 3, wherein said powder comprises a borosilicate glass.
 5. The method of claim 1, wherein said filling material comprises a room temperature liquid phase monomer of a thermoset polymer and said sufficient temperature results in heating said monomer above its cure temperature to result in crosslinking to form said thermoset polymer.
 6. The method of claim 1, further comprising chemical mechanical polishing (CMP) to smooth a top surface or a bottom surface of said plurality of interposer substrates.
 7. The method of claim 1, further comprising forming a wiring layer on at least one of a top side and a bottom side of said plurality of interposer substrates for customizing a routing pattern provided.
 8. A method of forming interposers, comprising: positioning a plurality of extruded copper wires across a first platten and second platten; adding sealing material to sidewalls of a volume having said plurality of extruded copper wires within and said first and second plattens as end plates to form a holding volume; filling said holding volume with a dielectric powder; heating said dielectric powder to a sufficient temperature to soften said dielectric powder to form a heat treated filled volume, and sawing said heat treated filled volume into a plurality of slices having a predetermined thickness to form a plurality of interposer substrates having a plurality of feed-thru conducting features provided by said plurality of extruded copper wires.
 9. The method of claim 8, wherein said dielectric powder comprises a borosilicate powder, said sufficient temperature is 650 to 900° C. and is at least a softening point of said borosilicate powder, wherein said sufficient temperature is below a melting point of said plurality of extruded copper wires.
 10. An interposer, comprising: a substrate having a plurality of through-vias; a dielectric liner lining said through-vias, and a plurality of feed-thru electrically conducting features provided by a plurality of extruded metal wires within said dielectric liner.
 11. The interposer of claim 10, wherein said extruded metal wires comprise extruded copper wires that are in direct physical contact with said dielectric liner.
 12. The interposer of claim 10, wherein said substrate is a dielectric material which provides said dielectric liner.
 13. The interposer of claim 12, wherein said dielectric material comprises a borosilicate glass.
 14. The interposer of claim 10, further comprising a wiring layer on at least one of a top side and a bottom side of said interposer for customizing a routing pattern provided. 